The present invention is related to a microphone circuit and relates more particularly to a feedback noise-eliminating microphone circuit which eliminates noises by means of the operation of positive-phase and reverse-phase pick-up circuits, positive-phase and reverse-phase amplifiers, and a balance adjusting circuit.
A microphone circuit according the prior art technique is generally comprised of a pick up circuit to pick up a sound source, an amplifier to amplify the signal detected by the pick up circuit, and a loudspeaker for the output therethrough of the signal amplified by the amplifier. The common disadvantage in regular microphone circuits is that a whistling noise tends to occur during operation. The whistling noise is produced due to feedback noise from the loudspeaker. When the volume is increased, the feedback noise will be increase too. A phasing circuit may be used to improve this problem, however, it still can not provide a satisfactory result.